County profile · official public datasets

Sanders County, MT

120 public highway bridges tracked in the FHWA National Bridge Inventory: 40% rated Good, 52.5% Fair, 7.5% Poor.

120
Public bridges: 40%
Good condition: 7.5%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Sanders County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

37th
of 56 on Poor share: 7.5%
Poor-condition share: 120
public highway bridges: 1979
avg year built

Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.

Sanders County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Sanders County ranks #37 of 56 Montana counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.5%). Sanders County, Montana contains 120 public highway bridges. Roughly 40% are rated “Good,” 52.5% “Fair,” and 7.5% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.

Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.

Source: FHWA National Bridge Inventory. See methodology for full definitions.

Total bridges

120

Public highway bridges in Sanders County

Good condition

40%

48 of 120 rated 7-9

Fair condition

52.5%

63 of 120 rated 5-6

Poor condition

7.5%

9 of 120 rated 4 or below

In-state Poor-share rank

#37 of 56

Among Montana counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 120 NBI-tracked bridges by lowest applicable component rating.

Good

40% (48)

Fair

52.5% (63)

Poor

7.5% (9)

Sanders County's Poor-condition bridges carry 4,651 vehicle crossings a day

That is 10.2% of the county's reported daily bridge traffic on 7.5% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 517 crossings a day against 348 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.

Computed over the 120 of 120 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

45.8% of Sanders County's bridges have passed the 50-year mark

55 of the 120 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 40% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.

Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.

One structure carries 52.4% of the county's Poor-condition bridge traffic

S 200 over CLARK FORK RIVER, built 1960, carries 2,436 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 9-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 4,651 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

1
1920s

2
1930s

1
1940s

1
1950s

16
1960s

25
1970s

21
1980s

9
1990s

16
2000s

15
2010s

13

What this shows Construction peaked in the 1960s, when 25 of the county's bridges still in the inventory were built, which is 20.8% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1979) matches the Montana average (1977).

How Sanders County compares with Montana's closest counties by inventory size

The 5 Montana counties nearest Sanders County in number of bridges, with their condition splits. Its 7.5% Poor share is the 4th-lowest of these 6. Its average build year of 1979 against a peer-group mean of 1979 is in line with the group.

Showing the 5 closest of 55 Montana counties eligible for comparison.

Bridge inventory size and condition shares for Sanders County and the 5 Montana counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Park County	124	21%	68.5%	10.5%	1976
Sanders County (this page)	120	40%	52.5%	7.5%	1979
Lake County	117	57.3%	27.4%	15.4%	1995
Rosebud County	114	18.4%	76.3%	5.3%	1973
Powell County	113	25.7%	68.1%	6.2%	1981
Dawson County	109	8.3%	85.3%	6.4%	1972

Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Sanders County's. Source: FHWA National Bridge Inventory, 2024 release.

Nationwide counties with similar inventory size or average build year

Two NBI-derived peer sets for Sanders County, both outside Montana so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside MT (120 bridges here).

Matanuska-Susitna County, AK · 120 bridges
Indian River County, FL · 120 bridges
Perry County, MO · 120 bridges
Schuyler County, MO · 120 bridges

Similar average build year

Nearest mean year-built outside MT (1979 here).

Pima County, AZ · avg 1979 · 1,150 bridges
Jefferson County, KY · avg 1979 · 662 bridges
Spartanburg County, SC · avg 1979 · 638 bridges
McPherson County, KS · avg 1979 · 586 bridges

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 120 Good 48 Fair 63 Poor 9

All bridges (120)

Sort:

Sanders County Bridge Snapshot

Condition distribution

Sanders County's Poor-condition bridges carry 4,651 vehicle crossings a day

45.8% of Sanders County's bridges have passed the 50-year mark

One structure carries 52.4% of the county's Poor-condition bridge traffic

How Sanders County compares with Montana's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (120)

RD 7670

NO DATA ENTERED

TROUT CREEK RD

RD 7593

NOXON AVE E

NO DATA ENTERED

RD 7593

RD 56

IRR - S 28

RD 153

RD 7583

RD 153

WHITEPINE CR RD

BEND RD

S 200

NO DATA ENTERED

RD 367

RD 7688

S 200

IRR - S 382

S 56 FH 5

NO DATA ENTERED

NO DATA ENTERED

S 200

S 200

NO DATA ENTERED

RD 7609

BLUE SLIDE RD

NO DATA ENTERED

RD 217

NO DATA ENTERED

RD 7670

LIL BITTERROOT RD

IRR - S 28

MARTEN CREEK RD

BIRDLAND BAY RD

S 200

EMERSON RD

S 56 FH 5

NO DATA ENTERED

NO DATA ENTERED

SLOAN RD

MARTEN CREEK RD

UPPER RIVER RD

BIG BEAVER CREEK R

BIG BEAVER CREEK R

LIL THOMPSON R RD

CHERRY CREEK RD

HEWOLF DR

S 471 FH 7

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